Pasteurization of liquid foods has the goal of destroying all pathogenic microorganisms in milk, notably Mycobacterium tuberculosis and other pathogens such as Brucella species, Salmonella or Escherichia coli bacteria. While pasteurization does reduce the number of viable vegetative bacteria by several orders of magnitude, it does not reduce the content of viable spores. Pasteurization of liquid foods such as milk, fruit juice or soups requires that the liquid be raised to a sufficiently high temperature for a sufficient length of time so as to render the liquid safe for consumption for a specified period of time known as shelf life. Continuous pasteurization systems for milk must meet prescribed parameters set by governmental authorities for temperature and duration at that temperature. The United States Food and Drug Administration (FDA), for example, has developed the Pasteurized Milk Ordinance (PMO) which requires milk to be raised to a temperature of about 162° F. (approximately 74° C.) for a minimum of 16 seconds. In view of the low intensity of a pasteurizing heat treatment, the nutritional quality of pasteurized milks is virtually unimpaired. Milk is no longer considered legal if untreated milk is later mixed with the pasteurized milk, and is unacceptable for sale and consumption if intermixed with cleaning liquids.
The conditions required for pasteurization of various foodstuffs may vary. For dairy processing, probably the most widely used process today is referred to in the art as a continuous high-temperature short-time (HTST) procedure, where the milk is rapidly (within a few seconds) heated to temperatures of about 74° C. and held for 15 to 20 seconds at this temperature as required by FDA standards. U.S. Pat. No. 6,136,362 describes such an HTST process.
HTST pasteurization is performed with plate heat exchangers transferring the heat across the metal wall from the heating medium (hot water) to the product (milk) or, in the regeneration section, from the outflowing heated milk to the incoming, cool milk. Between the heating and the cooling section, a holding tube is inserted to provide the necessary holding time of the milk at the pasteurization temperature. The heated milk flows through the cooling section where it is cooled with ice water or brine.
These processes of course may be varied depending on the liquid food being pasteurized. For example, cream requires higher temperatures for effective destruction of harmful microorganisms.
Milk is supersaturated in calcium and phosphate by virtue of the ability of the casein micelle to keep micelle-linked calcium phosphate in a colloidal state. In the milk serum calcium is mainly chelated by citrate ions, and, to a lesser extent, by phosphate ions.
When milk is heated, the pH is lowered due to lactose degradation and the formation of organic acids, such as formic acid. Tricalcium phosphate is formed and some of it may be precipitated from the milk. Calcium phosphate deposits on heat exchangers and in evaporators (fouling) are frequently occurring in dairy plants and are formed during the processing of milk as well as of whey. The deposits usually are not purely mineral but also contain significant amounts of protein. This reaction is responsible for the formation of calcium phosphate deposits during storage of UHT milks.
Such protein soil residues occur in all types of food processing equipment, but are particularly common with milk and milk products which are high in proteins, and may be left on the surfaces of pasteurizing equipment. Furthermore, it is particularly important with milk and milk products to remove such soil because dairy products are among the most perishable of major foodstuffs and soil residues may have serious quality consequences.
Residual protein soil left on food contact equipment surfaces can harbor and nourish the growth of opportunistic pathogen and food spoilage microorganisms. These pathogen and microorganisms can contaminate foodstuffs processed in close proximity to the residual soil. Insuring protection of the consumer against potential health hazards associated with food borne pathogens and toxins requires diligent cleaning and soil removal from any surface that contacts the food product directly or any surface that is associated with the processing environment.
Because of food quality concerns and public health pressures, the food processing industry has attained a high standard of practical cleanliness and sanitation.
There remains a need in the industry, however, for more effective and safe compositions suitable for removing proteinaceous soils, and for more efficient and less costly methods of achieving the soil removal goals as set by industry and government standards.